全文获取类型
收费全文 | 1879篇 |
免费 | 87篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 24篇 |
综合类 | 13篇 |
化学工业 | 516篇 |
金属工艺 | 33篇 |
机械仪表 | 36篇 |
建筑科学 | 123篇 |
矿业工程 | 4篇 |
能源动力 | 41篇 |
轻工业 | 113篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 112篇 |
一般工业技术 | 375篇 |
冶金工业 | 211篇 |
原子能技术 | 20篇 |
自动化技术 | 339篇 |
出版年
2023年 | 19篇 |
2022年 | 20篇 |
2021年 | 40篇 |
2020年 | 43篇 |
2019年 | 36篇 |
2018年 | 46篇 |
2017年 | 25篇 |
2016年 | 48篇 |
2015年 | 39篇 |
2014年 | 76篇 |
2013年 | 99篇 |
2012年 | 101篇 |
2011年 | 156篇 |
2010年 | 95篇 |
2009年 | 78篇 |
2008年 | 89篇 |
2007年 | 84篇 |
2006年 | 77篇 |
2005年 | 48篇 |
2004年 | 55篇 |
2003年 | 44篇 |
2002年 | 54篇 |
2001年 | 32篇 |
2000年 | 32篇 |
1999年 | 42篇 |
1998年 | 74篇 |
1997年 | 51篇 |
1996年 | 32篇 |
1995年 | 29篇 |
1994年 | 28篇 |
1993年 | 19篇 |
1992年 | 19篇 |
1991年 | 15篇 |
1990年 | 19篇 |
1989年 | 20篇 |
1988年 | 16篇 |
1987年 | 22篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1972年 | 7篇 |
排序方式: 共有1967条查询结果,搜索用时 15 毫秒
1.
2.
Dynamic complexity investigates the required effort to maintain knowledge about a property of a structure under changing operations.
This article introduces a refined notion of dynamic problems which takes the initial structure into account. It develops the
basic structural complexity notions accordingly. It also shows that the dynamic version of the LOGCFL-complete problem D2LREACH(acyclic) can be maintained with first-order updates. 相似文献
3.
We propose a space-efficient scheme for summarizing multidimensional data streams. Our sketch can be used to solve spatial
versions of several classical data stream queries efficiently. For instance, we can track ε-hot spots, which are congruent
boxes containing at least an ε fraction of the stream, and maintain hierarchical heavy hitters in d dimensions. Our sketch
can also be viewed as a multidimensional generalization of the ε-approximate quantile summary. The space complexity of our
scheme is O((1/ε) log R) if the points lie in the domain [0, R]d, where d is assumed to be a constant. The scheme extends to the sliding window model with a log (ε n) factor increase in
space, where n is the size of the sliding window. Our sketch can also be used to answer ε-approximate rectangular range queries
over a stream of d-dimensional points. 相似文献
4.
Das Autobahnmautgesetz zeichnet sich durch eine strenge Zweckbindung für die Mautdaten aus. Diese dürfen ausschlie?lich für
die Zwecke des Mautgesetzes erhoben und verarbeitet werden. Diese Vorgabe hat das LG Magdeburg in einem Beschluss richtungsweisend
auch für die Verbindungsdaten der GSM-Kommunikation best?tigt. 相似文献
5.
Volker Mayer 《Dynamical Systems: An International Journal》2007,22(2):169-178
We prove several essential fractal properties, such as positivity, finiteness or local infinity, of Hausdorff and packing measures of radial Julia sets for large subclasses of entire and meromorphic functions considered in our previous work: çGeometric thermodynamical formalism and real analyticity for meromorphic functions of finite order'. Most of the results proven are shown to be optimal. 相似文献
6.
7.
8.
The homopolyester of 4-(4′-hydroxyphenoxy)benzoic acid (poly(4-HPBA)), was prepared under two different reaction conditions and compared with a sample provided by another research group. Depending on the synthetic route, different melting points, d.s.c. traces and crystal lattices were found. However, after repeated heating and cooling, one thermodynamically stable modification with a melting point of 370–375°C can be obtained. Copolyesters of 4-hydroxybenzoic acid and 4-(4′-hydroxyphenoxy)benzoic acid were prepared with various molar ratios either in the melt (condensation in bulk) or in solution. These copolyesters were characterized by elemental analyses, 1H n.m.r. spectroscopy, d.s.c. measurements, wide-angle X-ray scattering measurements at various temperatures, and optical microscopy. Whereas copolyesters prepared in solution do not melt below 500°C, those prepared by polycondensation in bulk show melting points down to approximately 260°C and form a nematic melt. 相似文献
9.
This paper presents an economically attractive system for the hierarchical evolution of High Definition Television (HDTV) compatible with the NTSC installed base. It describes the two main signals of this system: HDMAC-60 and HDNTSC. The first, HDMAC-60, is a feeder signal for use between the program origination and program redistribution points, and used also as a DBS emission format. The second, HDNTSC, is a delivery signal for high definition terrestrial broadcast, CATV distribution and VCR plus laser video disc applications. We propose this emission system as a means for transmitting HDTV pictures to consumers on the North American continent. 相似文献
10.